Aim of the work in progress is to examine several aspects of motor and sensory laterality in order to broaden our understanding of manual and hemispheric lateralization in man. The project is primarily addressed to laterality phenomena in normal adults and children, not in brain-injured patients who have already sustained impairment in motor and sensory function. Measures of brain asymmetry will be based on new techniques of simultaneous stimulation in audition (dichotic listening) and in vision (visual half-field stimulation). These developments in simultaneous stimulation will provide a unique and valid approach to the study of hemispheric asymmetry in non-brain-injured subjects. Initial experiments will examine additional stimulus and procedural parameters with these techniques in order to pin down the mechanisms which subserve these functional hemispheric asymmetries. The second phase of the project will focus on a number of variables which seem to be intrinsically associated with hemispheric lateralization--namely, handedness, familial handedness (i.e., sinistrality), age and childhood dyslexia. Each of these problems will be investigated in detail using different combinations of within-modal and cross-modal measures of asymmetry. Handedness will be quantitatively assessed in order to see whether dimensions of manual laterality interact with levels of hemispheric specialization. Major attention will also be addresssed to the investigation of hemispheric specialization of "nonlanguage" functions. This emphasis will broaden the scope of the study by permitting an examination of possible differences in the hemispheric organization of both speech/language and perceptual functions. These objectives are intended to provide a broader conceptual framework for lateral development in man.